JCSDA Community Radiative Transfer Model (CRTM) Framework

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JCSDACommunity Radiative Transfer Model (CRTM)
Framework
Yong Han, Quanhua Liu, Paul van Delst

JCSDA 3rd Workshop on Satellite Data
Assimilation, 20-21 April 2005
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Overview

• User Interface
• Forward, tangent-linear, adjoint, K-matrix
  (Jacobian)
• Public data structures
• Developer Interface
• The components
• Internal data structures
• Changes required for analytical Jacobians
• Shared Data
• What are they? How to use them?
• Shared data structures
• Testing
• Code test software and datafiles.
• Comparison with obs. Testing in GDAS.
• Utilities and Feedback

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What is the CRTM Framework?

• At the simplest level, its a collection of
  structure definitions, interface definitions, and
  stub routines.
• There are User and Developer interfaces, as well
  as Shared Data interfaces. (I/O functions for
  convenience).

Why do this?

• The radiative transfer problem is split into
  various components (e.g. gaseous absorption,
  scattering etc). Each component defines its own
  structure definition and application modules to
  facilitate independent development.
• Want to minimise or eliminate potential software
  conflicts and redundancies.
• Components developed by different groups can
  simply be dropped into the framework.
• Faster implementation of new science/algorithms.

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User Interface
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Current Forward CRTM Interface
Error_Status CRTM_Forward( Atmosphere,
Surface,
GeometryInfo,
ChannelInfo,
RTSolution )

• All data contained in structures.
• Additional arguments can be added as required
  to the requisite structures.
• No impact on calling routine.

Allowable dimensionality L number of channels
M number of profiles
INPUTS INPUTS INPUTS OUTPUTS
Atmosphere Surface GeometryInfo RTSolution
Scalar Scalar Scalar L
M M M L?M
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Example Definition of Atmosphere Structure
TYPE, PUBLIC CRTM_Atmosphere_type ! --
Dimension values INTEGER Max_Layers 0 !
K dimension INTEGER n_Layers 0 ! Kuse
dimension INTEGER n_Absorbers 0 ! J
dimension INTEGER Max_Clouds 0 ! Nc
dimension INTEGER n_Clouds 0 ! NcUse
dimension INTEGER Max_Aerosols 0 ! Na
dimension INTEGER n_Aerosols 0 ! NaUse
dimension ! -- Climatology model associated
with the profile INTEGER Climatology
INVALID_MODEL ! -- Absorber ID and units
INTEGER, DIMENSION( ), POINTER Absorber_ID
gt NULL() ! J INTEGER, DIMENSION( ), POINTER
Absorber_Units gt NULL() ! J ! -- Profile
LEVEL pressure and LAYER quantities REAL(
fp_kind ), DIMENSION( ), POINTER
Level_Pressure gt NULL() ! K REAL( fp_kind ),
DIMENSION( ), POINTER Pressure gt
NULL() ! K REAL( fp_kind ), DIMENSION( ),
POINTER Temperature gt NULL() ! K REAL(
fp_kind ), DIMENSION( , ), POINTER Absorber
gt NULL() ! K x J ! -- Clouds associated
with each profile TYPE( CRTM_Cloud_type ),
DIMENSION( ), POINTER Cloud gt NULL() !
Nc ! -- Aerosols associated with each profile
TYPE( CRTM_Aerosol_type ), DIMENSION( ),
POINTER Aerosol gt NULL() ! Na END TYPE
CRTM_Atmosphere_type
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PUBLIC CRTM Data Structures
Type Name Description
CRTM_ChannelInfo_type Sensor channel information filled during initialisation.
CRTM_Atmosphere_type Atmospheric state profile data. Contains Cloud and Aerosol structures.
CRTM_Surface_type Surface type and state information. Contains SensorData structure.
CRTM_GeometryInfo_type Earth location, zenith and azimuth angles.
CRTM_RTSolution_type Radiative transfer results.
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Current K-Matrix CRTM Interface
Error_Status CRTM_K_Matrix( Atmosphere,
Surface,
RTSolution_K,
GeometryInfo,
ChannelInfo,
Atmosphere_K,
Surface_K,
RTSolution )

• Same structure definitions for both the forward
  and K-matrix structures.
• Channel dependencies are handled via the
  structure array dimensions.

Allowable dimensionality L number of channels
M number of profiles
INPUTS INPUTS INPUTS OUTPUTS OUTPUTS
Atmosphere Surface RTSolution_K GeometryInfo Atmosphere_K Surface_K RTSolution
Scalar L Scalar L L
M L?M M L?M L?M
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Developer Interface
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The CRTM Components

• Absorption by atmospheric gaseous constituents,
  e.g. water vapour, ozone, etc. AtmAbsorption
  functions.
• Compact-OPTRAN is currently used.
• OPTRAN-v7 has been implemented.
• OSS has been implemented.
• Scattering and absorption. AtmScatter functions.
• Aerosols
• Clouds
• Surface Optics. SfcOptics functions.
• Emissivity (land, ocean ?W, IR ice, snow,
  water, etc)
• Reflectivity (diffuse and direct)
• Radiative Transfer. RTSolution functions.
• Fixed multi-stream models
• SOI model

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INTERNAL CRTM Data Structures

• Not visible via the User Interface
• Developers modify the structure contents as
  needed
• Some components are mandatory and must be
  supplied others are algorithm specific.

Type Name Description
CRTM_AtmAbsorption_type Gaseous absorption optical depths and related parameters.
CRTM_AtmScatter_type Scattering parameters such as single scatter albedo, asymmetry factor, optical depths, etc.
CRTM_SfcOptics_type Surface optical properties such as emissivity and reflectivity.
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Example Definition of AtmScatter Structure
TYPE, PUBLIC CRTM_AtmScatter_type ! --
Dimension values INTEGER n_Layers
0 ! K dimension INTEGER Max_Legendre_Terms
0 ! Ic dimension INTEGER n_Legendre_Terms
0 ! IcUse dimension INTEGER
Max_Phase_Elements 0 ! Ip dimension INTEGER
n_Phase_Elements 0 ! IpUse dimension !
Algorithm-specific members REAL( fp_kind ),
DIMENSION( , , ), POINTER
Phase_Coefficient gt NULL() ! Mandatory
members REAL( fp_kind ), DIMENSION( ),
POINTER Optical_Depth gt NULL() ! K
REAL( fp_kind ), DIMENSION( ), POINTER
Single_Scatter_Albedo gt NULL() ! K REAL(
fp_kind ), DIMENSION( ), POINTER
Asymmetry_Factor gt NULL() ! K REAL(
fp_kind ), DIMENSION( ), POINTER
Delta_Truncation gt NULL() ! K END TYPE
CRTM_AtmScatter_type
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INTERNAL CRTM Functions

• Stub functions are provided for each component.
  Empty shell routines with the required structure
  arguments.
• Each component contained within its own module
  (or module hierarchy)
• Developers modify the contents of the application
  function. Can also include other dependent module
  subprograms, or other modules.
• Interfaces dont change (eventually!), so impact
  of a particular component update (e.g. the
  gaseous absorption algorithm replace OPTRAN
  with OSS) on the code is minimised.
• This is an ideal characterisation, as there may
  be dependencies between components (e.g. scaling
  of polychromatic gas absorption optical depths in
  the radiative transfer functions.)

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Changes still to be made

• Modifications for analytic Jacobians
• CRTM design was based on forward ? tangent-linear
  ? adjoint ? K-matrix approach.
• For analytic Jacobians, the K-matrix structures
  need to be passed in/out of the forward model
  call.
• Example Computation of gaseous absorption.
• Current forward model interface,
• Interface update,
• K-Matrix structure is declared as an optional
  output argument for the analytic Jacobians.

iErr CRTM_Compute_AtmAbsorption( Channel_Index,
AtmAbsorption )
iErr CRTM_Compute_AtmAbsorption( Channel_Index,
AtmAbsorption,
AtmAbsorption_K
AtmAbsorption_K )
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Shared Data
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The CRTM Shared Data

• Shared Data is the precomputed data that is
  loaded during the model initialisation. The
  shared data is loaded into a public data
  structure that can then be used by application
  modules.
• Shared data is not visible via the User
  Interface.
• Needed for
• Gaseous absorption functions require regression
  coefficients (e.g. OPTRAN) or optical depth
  lookup tables (e.g. OSS)
• Surface optics functions requiring coefficients
  (e.g. IRSSEM)
• Scattering functions may require the same (e.g.
  current aerosol absorption/scattering uses
  channel based coefficients, but will transition
  to spectra)
• Accessed by USE of the required shared data
  module.
• Getting data into the system is one of the more
  difficult parts of CRTM development (IMO).

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Current Shared Data CRTM Data Structures
Type Name Description
SpcCoeff_type Channel frequencies, polarisation, Planck function coefficients, etc.
TauCoeff_type Coefficient data used in the AtmAbsorption functions.
AerosolCoeff_type Coefficient data used in the AerosolScatter functions.
ScatterCoeff_type Coefficient data used in the CloudScatter functions.

• Will need the same for surface optics functions
  to compute surface emissivities/reflectivities.

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Testing Software
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Testing Outline

• Data
• Simple data initially.
• Atmosphere data from ECMWF 52 profile set.
• Cloud and Surface data from Quanhua Liu.
• Aerosol data from Clark Weaver.
• Collocated surface, atmosphere and satellite
  observations.
• Test instruments.
• Infrared AIRS (hyperspectral) and HIRS
  (broadband)
• Microwave AMSU (crosstrack scanner) and WindSat
  (polarimetric conical scanner)
• Anticipate three phases of testing
• Code testing using above simple datafiles.
• Comparison with theoretical results and satellite
  observations.
• Impact of CRTM on forecast skill.

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Testing Software

• Want to test each CRTM component (gaseous
  absorption, scattering, etc) in each model
  (Forward, K-matrix, etc) for consistency, as well
  as the end-to-end test.
• Have some initial attempts based on pCRTM and
  OPTRAN integration into CRTM.
• Forward/Tangent-linear check.
• Tangent-linear/Adjoint check
• Adjoint/K-matrix check.
• Each test type has a defined structure that is
  filled and dumped to file.
• Some rudimentary visualisation tools using IDL.
• The same structure definitions and file I/O is
  also used in the pCRTM tests the IDL code can
  view these also.

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FWD/TL test results for AtmAbsorption
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TL/AD test results for AtmAbsorption
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TL/AD test results for the pCRTM
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Utilities/Feedback
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Utilities/Feedback

• What generic utilities are needed for the CRTM?
• Example Planck functions.
• Others?
• HG phase function computation routines?
• Matrix operations/linear algebra libraries?
• Other source functions (e.g. for NLTE)?
• Feedback
• What do developers need?
• How is the current setup working?
• Easy to obtain and share software?
• Easy to obtain and share data?
• Sufficient documentation? Is the website
  sufficient? Deficient?
• What do we need to do to make development,
  testing, and integration of CRTM components
  easier?
• Looking at SourceForge as a home for CRTM
  developers.